A plurality of pulleys and a V-ribbed belt wrapped around the pulleys have widely been used as an accessory drive belt transmission system provided in an engine compartment of an automobile.
In such an accessory drive belt transmission system, when the automobile is running in rain, and water that entered the engine compartment comes between the V-ribbed belt and the pulley, the V-ribbed belt easily slips on the pulley, thereby generating slip sound. Various solutions to this problem have been proposed.
Patent Document 1 teaches a V-ribbed belt having a compression rubber layer made of a rubber composition prepared by blending 1-15 parts by mass of very short fiber having a length of 0.1-1.0 mm, and a moisture content of 6-20% relative to 100 parts by mass of rubber. This alleviates the slip of the belt even when water is present, and keeps the anti-slip effect continuously.
Patent Document 2 teaches a V-ribbed belt having a ribbed portion which contains at least short cotton fiber, and intermediate short fiber having an intermediate elastic modulus between an elastic modulus of rubber primarily constituting the ribbed portion, and an elastic modulus of the short cotton fiber. With this configuration, the short cotton fiber absorbs water on the belt, and a coefficient of friction smoothly changes as the wet belt dries. Further, the intermediate short fiber having the intermediate elastic modulus between the elastic modulus of the rubber and the elastic modulus of the short cotton fiber can prevent abrupt stick-slip friction, thereby preventing repeated slip and stick, and alleviating generation of noise.
Patent Document 3 teaches a V-ribbed belt in which a compression rubber layer is made of a rubber composition containing rubber, and 5-60 parts by weight (pbw) of hollow short fiber relative to 100 pbw of the rubber. This alleviates reduction in transmission performance when the belt is wet, and provides the V-ribbed belt with high resistance to wear, and high endurance.